The invention relates generally to fuel cells, and more particularly to reinforcing the polymer membranes used in fuel cells and to methods of making reinforced polymer membranes such that structural properties of such membranes are enhanced.
Fuel cells, also referred to as electrochemical conversion cells, produce electrical energy by processing reactants, for example, through the oxidation and reduction of hydrogen and oxygen. Hydrogen is a very attractive fuel because it is clean and it can be used to produce electricity efficiently in a fuel cell. The automotive industry has expended significant resources in the development of hydrogen fuel cells as a source of power for vehicles. Vehicles powered by hydrogen fuel cells would be more efficient and generate fewer emissions than today's vehicles employing internal combustion engines.
In a typical fuel cell system, hydrogen or a hydrogen-rich gas is supplied as a reactant through a flowpath to the anode side of a fuel cell while oxygen (such as in the form of atmospheric oxygen) is supplied as a reactant through a separate flowpath to the cathode side of the fuel cell. Catalysts, typically in the form of a noble metal such as platinum, are placed at the anode and cathode to facilitate the electrochemical conversion of the reactants into electrons and positively charged ions (for the hydrogen) and negatively charged ions (for the oxygen). In one well-known fuel cell form, the anode and cathode may be made from a layer of electrically-conductive gas diffusion media (GDM) material onto which the catalysts are deposited to form a catalyst coated diffusion media (CCDM). An electrolyte (also referred to as an ionomer, proton-transmissive or proton-conducting) layer separates the anode from the cathode to allow the selective passage of positively charged ions to pass from the anode to the cathode while simultaneously prohibiting the passage of the generated electrons, which instead are forced to flow through an external electrically-conductive circuit (such as a load) to perform useful work before recombining with the charged ions at the cathode. The combination of the positively and negatively charged ions at the cathode results in the production of non-polluting water as a by-product of the reaction. In another well-known fuel cell form, the anode and cathode may be formed directly on the electrolyte layer to form a structure known as a cathode coated membrane (CCM). Regardless of whether the configuration is CCDM-based or CCM-based, the resulting combination of one or more of the electrodes affixed to one or both opposing sides of the proton-conductive medium is known as a membrane electrode assembly (MEA).
One particular fuel cell configuration, known as the proton exchange membrane or polymer electrolyte membrane (in either event, PEM) fuel cell, has shown particular promise for vehicular and related mobile applications. The proton-conductive membrane that makes up the electrolyte layer of a PEM fuel cell is in the form of a solid (such as perfluorosulfonic acid (PFSA) layer of ionomer, a commercial example of which is Nafion®). An MEA; such that mentioned above, when configured to receive reactants through an appropriate flowpath (such as from a bipolar plate or other fluid delivery device), forms a single PEM fuel cell; many such single cells can be combined to form a fuel cell stack, increasing the power output thereof. Multiple stacks can be coupled together to further increase power output.
Despite advancements, one of the problems with existing PEM fuel cell technology is that forming an MEA from a free-standing electrolyte layer is expensive.